Elon Musk's Hyperloop hype ignores practical problems

August 15, 2013
by Troy Wolverton, San Jose Mercury News

You've got to hand it to Elon Musk - he certainly dreams big. The entrepreneur loves to take on tough technical challenges and turn them into business opportunities. He revolutionized online payment services with PayPal, built the first successful electric-car company with Tesla Motors and launched one of the first commercial space transportation companies with SpaceX.

But his proposed Hyperloop transportation system - which he unveiled Monday as a faster and lower-cost alternative to a high-speed train service between San Francisco and Los Angeles - may prove to be his toughest challenge yet. While the science behind the idea seems sound, turning it into reality would require overcoming a host of engineering design obstacles, not to mention political and funding hurdles.

"The high-level concept doesn't violate any fundamental laws of physics," John Hansman, a professor of aeronautics and astronautics at MIT, said Tuesday in an interview. But he added, "I'm not sure whether the details work."

The Hyperloop would consist of carlike capsules traveling at near the speed of sound through enclosed tubes. The capsules, which would contain about 28 passengers each, would ride on pockets of air, propelled by a linear induction motor. They would travel through a low-pressure air system that would limit resistance and friction without requiring the amount of energy needed to maintain a complete vacuum.

According to Musk, the system would cost just $6 billion and get passengers from Los Angeles to San Francisco in 35 minutes - less than one-tenth the price of California's proposed high-speed rail system, while moving passengers five times as fast.

At first blush, the concept seems to come from the realm of pulp sci-fi novels. It reminded me of a comic book I had as a kid in which a character traveled from Los Angeles to Tokyo on a high-speed train that traveled through a tunnel deep inside the Earth.

But as fantastic as the Hyperloop concept may appear, experts familiar with the 57-page proposal Musk unveiled Monday say it's theoretically feasible.

Linear induction motors already are used to propel maglev trains in Japan. Hovercraft have long demonstrated that one can travel on a pocket of air. And the first subway in New York was operated inside a pneumatic tube, which was a larger variation on the systems still used by consumers at drive-up bank windows and pharmacies.

"There's no question we have the technology to get something like this up and running," said James Moore, director of the transportation engineering program at the University of Southern California.

But while Musk has laid out the potential price of building the Hyperloop, he has ignored the development costs, which are likely to dwarf the cost of construction. Moore compared it to a pharmaceutical company exploring a new drug.

"It's not the manufacturing costs worrying them," he said. "The costs they're worried about are the development costs." A big part of that development cost would be to build a prototype that would highlight for engineers things Musk didn't account for or anticipate in his proposal, things that could come out only in real-world tests.

One concern would be how the fast-moving capsules would respond to even a slight misalignment in the tubes, said MIT's Hansman. Another would be the interplay between the low-pressure air in the tube and the air pads on which the capsule will ride, he said.

By laying out his proposal before actually prototyping it, Musk has skipped a crucial step, argued Richard Muller, a physics professor at the UC Berkeley.

"From the science point of view, he's done it the wrong way," Muller said.

Even if the Hyperloop idea proves sound in prototyping, practical issues would need to be overcome. A big one is how much energy the Hyperloop would require. The linear propulsion system and the air pressure pumps for the tubes would probably need much more energy than would be provided by the solar panels Musk proposes installing on the tubes and the energy recovery system he envisions having at the end of the route, said Roger Goodall, a maglev train expert and a professor of control systems engineering at the United Kingdom's Loughborough University.

Then there are safety concerns. Muller argues that the system, because of its novelty and the vulnerability of its tubes, would make a tempting target for terrorists. But it also could potentially be disrupted by more mundane threats, such as dirt and grime, he said.

And what would happen, Hansman wondered, if the power went out while a capsule was rocketing through the tube or if a capsule got stranded miles from a city?

Engineers would need to determine exactly how the Hyperloop would deal with such contingencies if the system is ever to get up and running.

While such challenges could be overcome, some experts are skeptical that they will be. Because Musk's proposal ignores the expense and risks of developing the Hyperloop, it is for now just "another science-fiction dream," Muller said. "It's completely impractical."

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43 comments

But while Musk has laid out the potential price of building the Hyperloop, he has ignored the development costs, which are likely to dwarf the cost of construction.

On the other hand, once you have developed it you can start to license/export it (which you can't do with bullet trains, as pretty much everyone and their grandmother has them by now).

By laying out his proposal before actually prototyping it, Musk has skipped a crucial step, argued Richard Muller, a physics professor at the UC Berkeley.

Definitely. Prototype needed.

The linear propulsion system and the air pressure pumps for the tubes would probably need much more energy

Not sure about the pumps. If the cylinder is even remotely airtight then a very modest pump arrangement can keep the low pressure stable (with many transportation shots it gets worse, as each introduces an air cushion which has to be removed subsequently. With 28 passengers per shot we're talking a LOT of shots per hour)

The hyperloop already succeeds in what it's designed to do: get people talking about Elon Musk.

Seriously. The guy even said he's not going to implement it since he's "too busy". The whole point is to get his other companies' stock up by the free advertizing and media articles as people argue about the proposal.

If the cylinder is even remotely airtight then a very modest pump arrangement can keep the low pressure stable

You forget that the cylinder is hundreds of miles long. If small sections leak just a little, the whole tube leaks like a seave, and maintaining the pressure the same across the whole tube is difficult because the air has to flow towards the pump from where it's leaking in, which won't happen in an instant across hundreds of miles. You get a pressure gradient away from the pumps.

The issue is, that the pumping becomes less effective the lower the pressure at the pump is, because each displacement cycle moves less and less air (mass). The pumps have to be distributed across the lenght of the tube to be effective in maintaining uniform low pressure, but then maintaining the pumps becomes a costly task because you increase the number of moving and failing parts.

Unlike with railroads, you can't just pop out of the capsule with a repair crew. You need maintenance roads

Richard Muller is the (ex) climate change denier who was paid by fossil fuel interests to study global temperature records in hopes he would prove climate scientist wrong, but came to the conclusion that the planet was, in fact, warming.

He may be an example of an extreme doubter.

I wonder if he actually read the paper. He certainly formed an opinion on climate change before he looked at the data....

and maintaining the pressure the same across the whole tube is difficult because the air has to flow towards the pump

The pump system must be distributed along the entire length in any case (as the vehicle rides on a cushion of air, which has to be subsequently removed. So the flow time/length towards a pump from a leak is minimal. Should also make leaks easily (and immedaitely) localiseable as pump at position X will have to work harder to maintain pressure levels.

Pumps aren't that complicated/costly (or prone to failure), so I'm not sure this is a real problem. In any case: there are systems that work with the opposite system. E.g. the Brazilian Aeromovel system - which has blowers and pumps for creating suction/overpressure along the entire line. This seems to be a rather robust setup. (Though the aeromovel lines are usually short (less than 10km))

as the vehicle rides on a cushion of air, which has to be subsequently removed

I thought the point was to use the speed of the vehicle to push air underneath it, as the tube maintains some air pressure and not a complete vacuum. In a sense, flying inside the tube like an ekranoplane.

Continuously pumping air in and then back out would be just a complete waste of energy.

The hyperloop already succeeds in what it's designed to do: get people talking about Elon Musk.

Seriously. The guy even said he's not going to implement it since he's "too busy". The whole point is to get his other companies' stock up by the free advertizing and media articles as people argue about the proposal.

You've got balls, Eikka, to denigrate Musk. He's sent privately funded rockets into space, which is no small feat, and will go down in history as the Henry Ford of the electric car. You, on the other hand, will be remembered for absolutely nothing.

This concept has been around for nearly a century and a half, AND prototyped. The skepticism of its feasibility is born out of the resentment that you will likely be dead before you see it come to fruition.http://www.nytime...tml?_r=0

1. The low pressure/vacuum of the tunnel seems to contradict the pressurized cushion of air the vehicle rides on. If the pressure is gained from the low pressure vacuum it's going to be extremely low efficiency/energy consumptive to maintain support of the vehicle and the constant loss of that pressure as the vehicle moves. Or if it rams the low pressure air sufficient to support the vehicle once high speed is reached, this means it also has to carry the mechanical means of bearing the vehicle until those speeds are reached - i.e. wheels or some other mechanical assist.2. The development cost engineering wise is probably minor compared to all political parasites that are going have there piece of flesh to support any such project, not to mention the efficiency losses of corrupt bidding processes again because of political cronyism.

If memory (of Musk's original paper) serves me right, there will be wheels on the vehicles. Sort of a landing gear apparatus. Although it sounded like these were more of a safety addon, the vehicle might ride on wheels until it reached a speed sufficient to ram the low pressure air and ride on the cushion.

Kinda like John Oliver said, "I got an idea, let's cure cancer - now you go do it." That's basically what Elon Musk has done with the whole hyperloop concept.

He's sent privately funded rockets into space, which is no small feat, and will go down in history as the Henry Ford of the electric car.

Ad-hominem. The fact that you worship the ground under his feet doesn't mean the man is omnipotent and everything he says is going to work.

And that's the whole point. So far he's just invented more gunpowder; whether his enterprises actually succeed to make something truly new and thrive, or go bust in the next ten years due to their practical infeasibility is yet to be seen.

If the pressure is gained from the low pressure vacuum it's going to be extremely low efficiency/energy consumptive to maintain support of the vehicle and the constant loss of that pressure as the vehicle moves.

If the vehicle is going to move at 900 km/h through the tube, a tiny amount of air will go a long way. The point is to have minimum air resistance while maintaining lift through the ground effect.

The idea is basically sound, because it solves the problem that completely evacuated tubes have: the need to levitate the car magnetically, which gets expensive due to the need for superconducting magnets. If you leave in a little bit of air, ordinary room temperature linear motors will do, and the air that gets squeezed in between the rail and the car will keep it afloat.

"The idea is basically sound, because it solves the problem that completely evacuated tubes have: the need to levitate the car magnetically," - Eikka

That's a 180 degree turn from your original accusation of "publicity stunt". And whether any project is successful in ten years depends on variables that are outside of the inventor's control, like the whims of financiers or competing technologies. History is full of tales of failure due to intrigue and self-interest. Tesla's free energy and the death of efficient public transportation by Robert Moses are just a couple of examples.

While it's not clear whether this could or couldn't work with the specs (especially the price) he envisions one has to admit two things:1) He's got a track record of proposing stuff that works2) He's got an image to lose by propsing something that is total BS. So I'm sure he had a few people check this out and work on before putting it out there.

The fast speed may be enough for the air cushion. I wonder how this handles during the acceleration/decelartion phases. Would be interesting to calculate what kind of additional pressure is needed to keep it floating at low speeds. It may be as simple as diverting some of the airstream that the propellers guide around the capsule. The pressure profile along the tube might not need to be uniform. Depending on what kind of freightweight there's certainly some finnicky controls at work.

Pressurized cabins are in order. A cabin breach on track would be fatal (but that's not so different from planes).

I still accuse Elon Musk for pulling off a publicity stunt, because he still has no intention of building the thing and expects others to pick up the ball (and bill).

How does it differ from any other research paper whre researchers propose something 8from space tethers to buidling solar cells with other materials, etc.). Are those publicity stunts, too?

The guy had an idea and is putting it out there. Why do you have a problem with that? To put it another way: What should he have done with the idea if he knows he's not going to build it? Patent it so no one can use it? Not tell anyone? I'm certain he likes his idea and would love to see it turned into a reality. Can't really fault him for broadcasting that.

Mostly because he's been re-implementing stuff that already works - to the extent that it is already proven to work before him.

2) He's got an image to lose by propsing something that is total BS.

Which is why -he- isn't attempting to implement it. It's exactly the same thing as with bunk science: you can always claim the other guy did it wrong when it fails. Besides, just as with his other "innovations", this too is basically a rehash of something that already exists - pneumatic trains and tube mail.

How does it differ from any other research paper whre researchers propose something 8from space tethers to buidling solar cells with other materials, etc.). Are those publicity stunts, too?

It differs in the fact that Elon Musk isn't a researcher - he's a venture capitalist - and he isn't publishing a research paper but a simple concept draft. If he was doing research, he'd have to prove something with the paper instead of just throwing out ideas and guessing costs.

I don't have problems with "putting out ideas", I have problems with this person worship cult in the making that is not unlike Apple and Steve Jobs, where anything he came up with was pure magic even if it wasn't really any different from an industrially designed soap box.

What would you have done if it had been your idea?

Actually put my money where my mouth is and done some preliminary computer simulations and prototyping before announcing the plan, and then not just leave it at that.

An example of how the media is building a person cult out of Elon Musk:

He revolutionized online payment services with PayPal

/He/ did not revolutionize anything. PayPal was born out of a merger of two existing online companies, one that developed online payments and pay processing, and another one which was focused on financing. Elon came from the financing company.

A prior competior, Billpoint, lost to PayPal because eBay bought them and limited the availability to only eBay auctions.

Built the first successful electric-car company with Tesla Motors

There were several at the beginning of the 20th century.

and launched one of the first commercial space transportation companies with SpaceX.

Keyword being "one of", because there's been commercial space transportation companies since the 1990's when the cold war ended and the US allowed commercial interest to orbit, since there was no more Soviet Union they could trade the technology with.

And how does this differ from the hyperloop idea? If it's already proven to work then looking at the idea - especially if it turns out to be able to save a ton of money - isn't bad.

The technology isn't new and unproven, but the implementation is. It's like saying "Let's build a 3 km tall skyscraper.". Skyscrapers exist - but nobody's built one that tall.

So? Did anyone say that this was a research paper?

You did draw parallels by asking the question.

And just as a reminder: The first journal/conference paper you write on any science project is also a concept draft.

But you don't publish your concept draft as if it was proper research, and you certainly don't go to national media and investors with a bunch of doodles and back-of-the-envelope calculations and say "I reckon this ought to work".

Anyone else would have been laughed out of the room, but since it's Elon, it's news, and any publicity is good publicity when you're selling something.

Still that question: What would you have done differently with the idea in his position?

The answer to that question depends on whether I had -any- intention of actually financing and building it.

If I had, then I would have been more thorough with the technical and financial analysis before going public with it. You know, show the feasibility of at least one crucial bit of it, because that would have been actual news.

If I hadn't, then I would have done exactly as Elon Musk, because it doesn't matter that nothing ever comes out of it - again the point is just to get everyone to chant your name in public, so more people would know you, so they would know your business and what you're trying to sell to them. Publicity attracts investors and sponsors, because publicity is contagious.

I'm certain he likes his idea and would love to see it turned into a reality. Can't really fault him for broadcasting that.

It's really the difference in rhetoric between selling the concept and selling yourself as the inventor of it. You can go to the public to say "I think this would be a good idea", and you can also go to the public to say "Look what I invented".

Let's say Michio Kaku proposed this concept instead of Elon Musk, in the same fashion that he did. He's a famous figure, authoritative, respected. How do you think the media would have handled him? They probably would have put him under the keel for not giving any more substance to the draft and for fishing for attention to sell another book.

" he has ignored the development costs, which are likely to dwarf the cost of construction".

Really? Several billion dollars of development? This is not like pharmaceutical companies where their research involves a large component of trial and error. The research will involve a lot of computer modelling with a few physical prototypes. I would be surprised if the final development bill came to more than a few billion.

It seems some journalist went to this professor to ask if he could find anything wrong with this project. These objections are so general they could be made over ANY project without a prototype. Let him make the calculations that Musk made an point out the faults.

For what? Intelligent people recognize BS at whatever stage of its realization.

That may be correct with supposed physics breakthrough devices like Andrea Rossi's E-Cat and his questionable demonstrations. But Elon Musk has only said this is do-able with technology we now have and It likely is, regardless of problem that need to be solved. This is no different than the last 50 years of space exploration ideas and proposals, of which quite a few have now been done.

A much more practical variation of the vacuum propulsion system was suggested over a hundred years ago and I recall reading somewhere that a prototype that worked was actually constructed in Italy but failed for lack of funding. They used a long tube containing a cylinder which pulled a wheeled train on its rails. The gap through which the tongue protruded was sealed with overlapping leather flaps. That is one design worth taking a second look at, considering that one could adapt a magnetic connection through a fully sealed vacuum tube propelling an electro-magnetic capsule. The train parts already exist, so development costs aren't as great as they might be.

Also keep in mind that Elon actually said, that he LIKES this idea, that HE thinks it is feasible and LESS expensive than alternatives. He also said that HE would build this project but is too busy with other projects (and YES HE IS!!!!). Finally he said that if no-one else picks up this project, then HE WOULD EVENTUALLY. So basically he wants to do this, but he has enough BIG projects already on his plate. FFS this man is an ACTION MAN, NOT A DREAMER!!!!! The world needs more ppl to make dreams come real, and Elon is doing just that!!! He could just sit back and live a life of luxury with his money, but NO, he wants to advance the world!! Also keep in mind his TESLA company isn't really churning out much profit, but he DOES license his technology to just about every electric car manufacturer in the world. So Elon is prepared to make a loss, or break even, if he can get technology moving to a practical stage and show the world it CAN BE DONE, rather than the usual negative attitudes.

Surely the heart of this idea is that the vehicle is very light, essentially a bubble, with no need for a strong and therefore heavy running assembly to manage the loads.Lightness allows a light weight tube structure and low power linear motor propulsion, to keep the heat generated down.Issues imho are passenger acceptance, as customers will spend a long time zipping through glorified sewage pipes, flexibility, as switching is not easy in this concept and tube sizing, because while a bigger tube has lots of efficiency advantages, a smaller tube is cheaper and may get built and then freeze the infrastructure into an undersized design, just as railways were hurt by Stephenson's use of the carriage gauge for rails.

How about ditching the low air pressure and pumping nightmare problems altogether? Use the tube as the outer part of a "jet engine", with the vehicle(s) inside acting like a moving compressor core(s), or it can be visualized as a "ducted fan" with a moving fan! Cylindrical segments of solar panels on the outside of the tubes will rotate in opposite direction, the gyroscopic forces will stabilize the tube, the rotation of the cylindrical solar cell segments will boost the sunlight power collected, according to a research about rotating solar cells i have read somewhere...and will keep them clean too, i suppose. Additional idea: bleed some of the air blast out the back of the vehicle to power the rotations of the solar cells segments!

Let's say Michio Kaku proposed this concept instead of Elon Musk, in the same fashion that he did. He's a famous figure, authoritative, respected. How do you think the media would have handled him? They probably would have put him under the keel for not giving any more substance to the draft and for fishing for attention to sell another book.

That's because Michio Kaku has no track record of proposing and *realizing* such ideas.

Musk has already taken on Detroit and space travel, two of the most difficult industries to ever try to break into. The Model S is *outselling* the Chevy Volt.

The world needs people who flout conventional wisdom. Google calls it "Moonshot thinking", and has a whole division dedicated to it.

There's a reason companies don't innovate. RISK. You do the thing you already know works -- even if it means building a $70 billion train system.

Musk, or someone, obviously needs to build a prototype. It's right to be skeptical. But not cynical.

The last criticisms cited by the article, safety concerns, are so ridiculous. What if the power goes out? What if a capsule gets stranded *MILES* from a city? Big deal! What if any of a thousand moving parts on an airplane fails midflight? Way worse in every way imaginable. Yet amazingly, airplanes work, they are extremely safe and millions of people use them every day. Obviously they aren't just going to slap this thing together without extensive development and testing. It will be proven safe long before passengers can buy a ticket. That's like saying, "maybe we shouldn't develop automobiles, what if someone ran out of gas on the road, or their brakes failed?"

The use of a miles-long tube maintained at a near-perfect vacuum for months. LHC is the largest such vessel yet. It teaches us how to create and maintain this vacuum in such a vessel of a size and scale and aspect ratio comparable to what musk is proposing.

Creating and maintaining a vacuum in such a vessel IS the most daunting tech hurdle, and the LHC is the closest thing yet to such a contraption.

I'm sorry if it is too big a concept to get your small mind around. Apparently musk's mind is a little bit bigger than yourshttps://www.faceb...p;type=3

We're talking about a 900 mile Indy track with an arc turn of 40 miles to return back

Since you'll stop where you're going there is no need to turn at full speed (there's really no point to do a 180° turn in any kind of transportation system at full speed, is there?).This needs a tube either way, The turnaround part can be anything from a turntable, to a low velocity half-turn to building the trains to be symmetrical.

And since this tube requires nowhere near the high vacuum needed in scientific apparatus the technical challenge isn't all that great. (such a high level vacuum would actually cause the system to fail)

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